1. Field of the Invention
The present invention relates to a method of forming a magnetic layer pattern, and a method of manufacturing a thin film magnetic head for manufacturing a thin film magnetic head comprising at least an inductive magnetic transducer for recording through the method of forming a magnetic layer pattern.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head mounted in a magnetic recording apparatus (for example, a hard disk drive) has been sought in accordance with an increase in the areal density of a magnetic recording medium (for example, a hard disk). As recording systems of the thin film magnetic head, for example, a longitudinal recording system in which a signal magnetic field is oriented in an in-plane direction (a longitudinal direction) of a hard disk and a perpendicular recording system in which the signal magnetic field is oriented in a direction perpendicular to a surface of the hard disk are well known. At present, the longitudinal recording system is widely used, but in consideration of market forces in accordance with an improvement in areal density, it is assumed that the perpendicular recording system instead of the longitudinal recording system holds promise for the future, because the perpendicular recording system can obtain advantages that higher linear recording density can be achieved, and a hard disk in which data has been already recorded has resistance to thermal decay effects.
The perpendicular recording system thin film magnetic head comprises, for example, a thin film coil generating a magnetic flux, and a pole layer emitting the magnetic flux generated in the thin film coil to the hard disk to perform a recording process. The pole layer includes an exposed surface exposed to an air bearing surface, and the exposed surface has, for example, a rectangular shape. In the thin film magnetic head, when a current flows into the thin film coil, a magnetic flux for recording is generated in the thin film coil. Then, when the magnetic flux is emitted from the pole layer to the hard disk, the hard disk is magnetized by a magnetic field (perpendicular magnetic field) for recording which is generated by the magnetic flux, so information is magnetically recorded on the hard disk.
In order to improve the recording performance of the perpendicular recording system thin film magnetic head, for example, it is required to minimize the effect of a failure generally called “side erasing”. Side erasing is a phenomenon in which when information is recorded on a track to be recorded (hereinafter simply referred to as “target track”) on the hard disk, information is also recorded on a track adjacent to the target track (hereinafter simply referred to “adjacent track”) without intention, thereby information which has been already recorded on the adjacent track is overwritten and erased.
Side erasing occurs mainly due to skew of the thin film magnetic head. The skew is a phenomenon in which when a suspension (which is a leaf spring holding a slider) is moved to a track direction during recording on the hard disk drive, the thin film magnetic head is slightly inclined toward the rotation direction of the hard disk, that is, an extending direction of tracks on the hard disk. When the thin film magnetic head is skewed, an unnecessary perpendicular magnetic field is generated by a magnetic flux concentrated onto a point except for an original recording point (trailing edge) corresponding to the target track in the pole layer, so the adjacent track is overwritten by the unnecessary perpendicular magnetic field. Therefore, in order to prevent an adverse effect by side erasing, for example, it is necessary to design the pole layer so that the occurrence of side erasing due to the skew can be prevented.
Therefore, some techniques regarding the structure and the manufacturing method of a thin film magnetic head capable of preventing the occurrence of side erasing due to the skew have been already proposed.
More specifically, for example, a pole layer including an exposed surface with a symmetrical inverted trapezoidal shape instead of a rectangular shape is known, and a technique of forming a pole layer having a configuration of this kind is also known. In the forming technique, after forming a photoresist pattern having an aperture so that the width of the aperture is gradually reduced toward the bottom through the use of the deformation effect of a photoresist by heating, the pole layer is formed by using the photoresist pattern (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2002-197611, 2002-197613 and 2002-197615).
FIGS. 37 through 40 are illustrations for describing steps of forming a conventional pole layer having an exposed surface with the above described symmetrical inverted trapezoidal shape in detail, and FIGS. 37 through 40 show sectional views parallel to an air bearing surface of a completed thin film magnetic head.
In order to form the pole layer, at first, as shown in FIG. 37, after a seed layer 102 is formed on a supporting substrate 101, a photoresist is applied to a surface of the seed layer 102 so as to form a photoresist film 103. Next, a mask 104 having an aperture 104K corresponding to the planar shape of the pole layer is used to pattern (expose and develop) the photoresist film 103 through photolithography, thereby as shown in FIG. 38, a photoresist pattern 105 having an aperture 105K with a substantially uniform width in a thickness direction (a Z-axis direction in the drawing) is formed. Then, the photoresist pattern 105 is heated, thereby as shown in FIG. 39, the photoresist pattern 105 is deformed so that the width of the aperture 105K is gradually reduced toward the substrate 101. Next, the seed layer 102 is used to selectively grow a plating film in the aperture 105K of the photoresist pattern 105, thereby a precursor pole layer 106Z is pattern-formed in the aperture 105K. Then, after removing the photoresist pattern 105, the seed layer 102 is selectively etched by using the precursor pole layer 106Z as a mask so as to remove an unnecessary portion (a portion not coated with the precursor pole layer 106Z) of the seed layer 102, as shown in FIG. 40. Finally, the precursor pole layer 106Z is polished from a side where an air bearing surface is formed to form the air bearing surface, thereby the pole layer including an exposed surface exposed to the air bearing surface is completed. The exposed surface of the pole layer has a shape corresponding to the shape of cross section of the precursor pole layer 106Z shown in FIG. 40, that is, a symmetrical inverted trapezoidal shape.
However, in the pole layer including the above exposed surface with a symmetrical inverted trapezoidal shape, for example, depending upon a skew angle (a tilt angle of the pole layer) determined on the basis of the structure of the hard disk drive, in the case where the shape of the exposed surface of the pole layer is designed in order to prevent the occurrence of side erasing due to the skew, if the area of the exposed surface is too small, an advantage that an adverse effect due to side erasing can be prevented can be obtained; however, the intensity of a magnetic field for recording declines due to a decrease in the amount of a magnetic flux emitted from the pole layer with a decrease in the area of the exposed surface, so overwrite characteristics which is one of important factors determining the recording performance of the thin film magnetic head may be degraded. The overwrite characteristics are characteristics that information recorded in the hard disk is overwritten with new information. Therefore, in order to stably secure the recording performance of the thin film magnetic head, it is necessary to establish a method of forming a pole layer capable of achieving compatibility between preventing the occurrence of side erasing due to the skew and securing the overwrite characteristics. In this case, specifically in consideration of mass production of the thin film magnetic head, it is important to establish a forming method capable of easily forming the pole layer through existing manufacturing processes.